Beverage making appliances are generally known. Among other things, beverage making appliances comprise a tube system for transporting a liquid, which may be a liquid to be used in a beverage making process as an ingredient of the beverage which is obtained as a result of the process. The liquid may be water, which is often used in beverage making processes. Another example of the liquid is milk.
The invention is applicable to various types of beverage making appliances, including appliances comprising a so-called milk frother. In general, frothing a liquid involves supplying a gas like air to the liquid and mixing the liquid with the gas, for the purpose of obtaining a mass of bubbles in the liquid, which is referred to as foam. Especially in the field of making coffee and coffee specialties, appliances are used which are capable of frothing milk in an automated manner. It is a well-known option to combine a frothing process of milk with a heating process of milk, wherein air is supplied to the milk for obtaining foam, and wherein steam is supplied to the milk for increasing the temperature of the milk.
In a practical embodiment, a milk frother comprises a jug for containing milk. During a milk frothing process, i.e. a process for making hot frothed milk, milk is sucked from the jug through a suction tube. Although the milk frothing process can be performed in a satisfactory manner, the application of the suction tube has a major drawback. The fact is that the suction tube is difficult to clean. Moreover, milk residue inside the suction tube dries up as time passes, so that the cleaning problem is even worse when there is a considerable time period between a last time that the milk frother was operated and a cleaning action. For sake of completeness, it is noted that a cleaning action normally involves rinsing the tube with water by forcing a quantity of water to flow through the suction tube, wherein the water may be at a high temperature in order to have an optimal cleaning effect.
US 2006/0174771 A1 discloses a milk frother which comprises a milk container, a foaming device and a valve assembly. The foaming device is provided with three channels, namely a steam supply channel, an air supply channel and a milk supply channel. The latter channel serves for transporting milk from the milk container to a mixing channel where the actual milk frothing process takes place during operation of the milk frother, and has a horizontally extending portion. Among other things, US 2006/0174771 A1 teaches that the foaming device is easy to clean and provides anti-microbial activity when the channels of the foaming device are provided with a surface constituted by nanoparticles, being both hydrophobic and oleophobic, wherein at least some of the nanoparticles consist at least partially of silver or a silver compound.
In respect of cleanability, it is furthermore taught that even if the milk frother is relatively unsusceptible to contamination, it should be cleaned regularly. In this respect, is it noted that cleaning can be performed by means of a flushing program in which at least the ducts, bores and channels which are critical as far as contamination is concerned are flushed with hot water. Another possibility as mentioned consists in lifting the foaming device off the milk container, so that it is possible to expose the inner parts of the foaming device which are critical as far as contamination is concerned, including the horizontally extending portion of the milk supply channel, and cleaning those parts in a dish washer.
US 2006/0174771 A1 is just one example of a document in which bothersome measures for cleaning a channel for transporting milk are described. The information as can be found in US 2006/0174771 A1 underlines the fact that cleaning such a channel normally involves rinsing of the channel on a regular basis. Also, it is demonstrated that costly measures can be proposed in an attempt to decrease the extent to which the channel gets contaminated with milk residue in the first place.